[MF] Advice for cuckold is needed

I had a long-term relationship with my gf. We broke up two month ago because of quarantine. We couldn’t manage distance, we live in different countries. But now everything is good between us, I have a gf already and she told me that she is in an open relationship with her ex now. And I really want to ask her to send me pics or videos with her ex fucking her. She knows about my fantasies, but we never tried anything related to cuckold sex. Is it okay if I ask her and how to do it better?